1. Field of the Invention
The invention pertains to a method for controlling the cut-off register wherein print control marks applied to a printed substrate are scanned to determine the actual positions of the marks, and the actual positions are compared with desired values to generate actuating signals for cut-off register control actuators.
2. Description of the Related Art
The cut-off register is usually controlled by the use of print control marks printed on the printed product. These marks are detected by sensors, and the actual values of the print control marks thus detected are compared with desired values for the print control marks, so that, on the basis of this comparison, actuating signals can be generated for controlling the cut-off register. These types of print control marks, which are printed on the product outside the actual printed image or subject, are undesirable especially in the case of newspaper printing, because in the case of newspapers the printed product is not cut and thus the print control marks are visible in the end product.
U.S. Pat. No. 6,779,454 discloses a process for cut-off register control on a printing press which does not work with marks. Here the printed image on the product is scanned by sensors. The actual values thus obtained are compared with desired values, which are based on image data or preliminary-stage printing data. In the case of markless cut-off register control using desired values based on preliminary-stage printing data, large amounts of data must be processed, the exact amount depending on the resolution of the preliminary data. Efficiency thus suffers. If preliminary-stage printing data of lower resolution are used, the control accuracy which can be achieved suffers.